mmc: sdhci-xenon: kill xenon_clean_phy()

Currently, the xenon_clean_phy() is only used for freeing phy_params.
The phy_params is allocated by devm_kzalloc(), there's no need to free
is explicitly.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Hu Ziji <huziji@marvell.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>